It is a common practice to provide a variety of phase difference films in a display device such as a liquid crystal display device.
As a method for producing a phase difference film, a method in which an isotropic primary film is stretched to impart optical anisotropy is widely used. However, with such a production method, it is difficult to produce a certain type of phase difference film. For example, it is difficult to obtain a film having an NZ factor of less than 1, such as a three-dimensional phase difference film, a negative A plate, and a positive C plate, by simply stretching an isotropic film.
As a method for obtaining a phase difference film having a small NZ factor, some methods have been proposed. As one of the methods, a method in which a primary film is bonded to a shrinkable film to obtain a layered film and the layered film is shrunk is known (for example, Patent Literature 1).